Related Experiment Video
Updated: Jun 22, 2026
12:18
Microwave Photonics Systems Based on Whispering-gallery-mode Resonators
Published on: August 5, 2013
Summary
Apodisation, or windowing, of coupling coefficients in coupled resonator waveguide devices (CROWs) effectively reduces secondary sidelobes in their bandpass characteristics. This technique, common in digital filters, enhances the performance of photonic devices.
Area of Science:
- Photonics
- Optical Engineering
- Filter Design
Background:
- Coupled Resonator Waveguide Devices (CROWs) are crucial for optical filtering.
- Secondary sidelobes in CROW transfer functions degrade filter performance.
- Traditional apodisation techniques are used in digital and photonic filters.
Purpose of the Study:
- To analyze the apodisation of coupling coefficients in CROW unit cells.
- To investigate the reduction of secondary sidelobes in CROW bandpass characteristics.
- To explore the application of windowing functions for improved CROW performance.
Main Methods:
- Apodisation (windowing) applied to coupling coefficients within CROW unit cells.
- Analysis of both Type-I and Type-II CROW structures.
- Evaluation using various standard windowing functions.
Main Results:
- Apodisation significantly reduces secondary sidelobe levels in CROW transfer functions.
- Different windowing functions offer varying degrees of sidelobe suppression.
- The technique is applicable to both Type-I and Type-II CROW designs.
Conclusions:
- Apodisation is a viable and effective method for suppressing secondary sidelobes in CROWs.
- Windowing coupling coefficients offers a practical approach to enhance CROW filter performance.
- This study provides insights for designing improved CROW-based optical filters.
Related Concept Videos
01:14Sound Waves: Resonance
Resonance is produced depending on the boundary conditions imposed on a wave. Resonance can be produced in a string under tension with symmetrical boundary conditions (i.e., has a node at each end). A node is defined as a fixed point where the string does not move. The symmetrical boundary conditions result in some frequencies resonating and producing standing waves, while other frequencies interfere destructively. Sound waves can resonate in a hollow tube, and the frequencies of the sound...
01:23Parallel Resonance
The parallel RLC circuit is an arrangement where the resistor (R), inductor (L), and capacitor (C) are all connected to the same nodes and, as a result, share the same voltage across them. The parallel RLC circuit is analyzed in terms of admittance (Y), which reflects the ease with which current can flow. The admittance is given by:
01:24Characteristics of Series Resonant Circuit
Series resonance occurs in a circuit containing inductive (L), capacitive (C), and resistive (R) elements connected sequentially. At the resonance frequency, the inductive and capacitive reactances are equal in magnitude but opposite in sign, effectively canceling each other. This causes the circuit's impedance is minimal, primarily determined by the resistance R. The resonant frequency of an RLC circuit is defined as:
01:28Standing Waves in a Cavity
A household microwave and lasers are examples of standing electromagnetic waves in a cavity. When two conducting metal plates are placed parallel at the nodal planes, it creates a cavity where standing waves are formed. The cavity between the two planes is analogous to a stretched string held at the points x = 0 and x = L. Here, the distance 'L' between the two planes must be an integer multiple of half of the wavelength. The wavelengths that satisfy this condition are given by:
01:07Propagation of Waves
When a wave propagates from one medium to another, part of it may get reflected in the first medium, and part of it may get transmitted to the second medium. In such a case, the interface of the two mediums can be considered as a boundary that is neither fixed nor free.
Consider a scenario where a wave propagates from a string of low linear mass density to a string of high linear mass density. In such a case, the reflected wave is out of phase with respect to the incident wave, however the...
Consider a scenario where a wave propagates from a string of low linear mass density to a string of high linear mass density. In such a case, the reflected wave is out of phase with respect to the incident wave, however the...
01:16Cascaded Op Amps
Operational amplifiers (op-amps) are versatile electronic components that can be interconnected in a cascade - one after another in a linear sequence. This cascading is possible due to their infinite input resistance and zero output resistance, allowing them to maintain their input-output relationships even when connected in series.
In a cascaded system, each op-amp is referred to as a stage. The output of one stage drives the input of the subsequent stage. As the input signal passes through...
In a cascaded system, each op-amp is referred to as a stage. The output of one stage drives the input of the subsequent stage. As the input signal passes through...